JPH0613073A - Cadmium negative electrode for alkaline storage battery - Google Patents

Abstract

PURPOSE:To extend the surface area of an electrode to increase O2 gas reacting part and improve O2 gas consuming performance by adding a reinforcing material not to the surface layer of the electrode but only to the electrode inner layer. CONSTITUTION:Cadmium oxide, Ni powder, a reinforcing material fiber, and ethylene glycol solution of carboxymethyl cellulose are kneaded together to prepare an active material paste. This is applied to a Ni-plated punched base for collector followed by heating and drying to form a cadmium oxide electrode. On the other hand, metal cadmium, carboxymethyl cellulose, fluorine resin dispersion, and ion exchange water are kneaded together to prepare a metal cadmium paste. This is applied to both surface of the cadmium oxide electrode followed by heating and drying to form a cadmium negative electrode. According to this negative electrode, since O2 gas generated at overcharge of battery can be quickly absorbed, an alkaline storage battery conforming to quick charge can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved cadmium negative electrode used in alkaline storage batteries.

[0002]

2. Description of the Related Art In recent years, in alkaline storage batteries, the paste type cadmium negative electrode has a
Since it has advantages such as a simple manufacturing process, low cost, and high energy density, it has been used more and more. However, the conductivity of the electrode is inferior to that of the sintered cadmium negative electrode, so that the oxygen gas generated from the positive electrode during overcharging is poorly absorbed, and when used in a sealed battery, the internal pressure of the battery tends to rise. It was
Therefore, a method of forming a cadmium negative electrode before incorporating it into a battery, forming metal cadmium as a discharge reserve amount, and imparting conductivity is adopted, but this method is simple in the manufacturing process of the paste type cadmium negative electrode. The cost advantage has been compromised.

[0003]

SUMMARY OF THE INVENTION In order to solve such a problem, Japanese Patent Laid-Open No. 54-50843 discloses that
It is said that by forming a layer of metal cadmium on the surface of the paste-like active material layer, the oxygen gas absorption performance is excellent and the chemical conversion step can be omitted. It was still insufficient in strength and oxygen gas absorption performance. On the other hand, it is possible to impregnate a paste-type cadmium negative electrode with a dispersion liquid of a fluororesin, to make the electrode active material water-repellent, to increase the reaction area between oxygen gas and the electrolytic solution, and to improve the oxygen gas absorption performance and the physical strength of the electrode. Although proposed, the oxygen gas absorption performance and the physical strength of the electrode equivalent to those of the sintered cadmium negative electrode have not yet been obtained.

The present invention overcomes these drawbacks of the prior art,
An object of the present invention is to obtain a cadmium negative electrode for alkaline storage batteries, which is relatively inexpensive and has excellent oxygen gas absorption performance and excellent physical strength of the electrode without chemical conversion in the manufacturing process of the paste type cadmium negative electrode.

[0005]

The present invention relates to a cadmium negative electrode having an inner layer mainly composed of cadmium oxide and a surface layer mainly composed of metal cadmium, the inner layer having a reinforcing material, and the surface layer Is a cadmium negative electrode for an alkaline storage battery, which has no reinforcing material.

[0006]

In general, the sealed nickel-cadmium battery is obtained by consuming oxygen gas generated from the positive electrode on the negative electrode during overcharge. This reaction occurs only when the surface of the negative electrode, the electrolytic solution and oxygen gas come into contact with each other. On the other hand, in order to maintain the strength of the electrode, a reinforcing material is added to the electrode, but in the present invention, the reinforcing material is added only to the electrode inner layer, and the surface layer of the electrode does not contain the reinforcing material. Since it can be made wider and the number of reaction sites that contribute to the oxygen gas reaction increases, the consumption capacity of oxygen gas will eventually improve.

[0007]

The present invention will be described in detail below with reference to examples. An active material paste obtained by kneading 95 parts by weight of cadmium oxide, 5 parts by weight of nickel powder, fibers as a reinforcing material, an ethylene glycol solution of carboxymethyl cellulose, and an ethylene glycol solution of polyvinyl alcohol is a current collector. It was applied on a nickel-plated punched substrate and dried at about 120 ° C. for 2 hours to obtain a cadmium oxide electrode. Then, a mixture of 100 parts by weight of metal cadmium, carboxymethyl cellulose, fluororesin dispersion and ion-exchanged water was kneaded to obtain a metal cadmium paste. This paste was applied to both surfaces of the cadmium oxide electrode and dried at about 150 ° C. to obtain a cadmium negative electrode a according to the present invention. As a comparative example of the electrode a according to the present invention, a cadmium negative electrode b having a surface layer obtained by adding fibers as a reinforcing material to a metal cadmium paste was prepared.

Batteries A and B were constructed by using these negative electrodes as known nickel paste positive electrodes. FIG. 1 shows the inside of the batteries when these batteries were overcharged at 1 C to 300% of the nominal capacity. Battery A showed a lower internal pressure than battery B. This is because the cadmium negative electrode of Battery A has no reinforcing material added to the electrode surface layer,
It is considered that the surface layer has a large porosity and the reaction site that consumes oxygen gas is wide.

[0009]

As described above, according to the present invention, the oxygen gas generated when the battery is overcharged can be quickly absorbed.
It is possible to obtain an alkaline storage battery with high industrial value that is compatible with quick charging.

[Brief description of drawings]

FIG. 1 is a comparative diagram showing changes in internal pressure of a battery due to overcharge.

[Explanation of symbols]

 A: battery of the present invention B: comparative battery

Claims (1)

[Claims] 1. An inner layer mainly composed of cadmium oxide,
A cadmium negative electrode having a surface layer containing metal cadmium as a main component, wherein the inner layer has a reinforcing material and the surface layer does not have a reinforcing material.